ACE (Advanced Composition Explorer)

A NASA satellite designed to measure the elemental and isotopic composition
of matter from several different sources, including the solar corona
and the interstellar medium.

ACE was placed in a halo orbit around
the first Lagrangian point (L1) of the
Earth-Sun system, about 1.4 million km from Earth. It carries six high-resolution
sensors and three monitoring instruments for sampling low-energy particles
of solar origin and high-energy galactic particles with a collecting power
10–1,000 times greater than previous experiments. The spacecraft can
give advance warning, of about one hour, of geomagnetic storms that might
overload power grids, disrupt communications, and pose a hazard to astronauts.